1. Field of the Invention
The present invention relates to a fundus oculi observation device, a fundus oculi image display device and a fundus oculi image display method that are used for observing the state of the fundus oculi of an eye.
2. Description of the Related Art
As a fundus oculi observation device, conventionally, a retinal camera has been widely used. FIG. 16 shows one example of the appearance of a conventional, general retinal camera, and FIG. 17 shows one example of an optical system configuration internally accommodated in the retinal camera (e.g. JP Patent laid-open No. 2004-350849). Herein, “observation” includes at least a case of observing produced fundus oculi images (observation of a fundus oculi with a naked eye may be included).
First, referring to FIG. 16, an explanation will be made regarding the appearance of a conventional retinal camera 5000. This retinal camera 5000 is provided with a platform 3 mounted on a base 2 so as to be slidable in the front and rear, right and left directions (horizontal direction). On this platform 3, an operation panel and a control lever 4 are installed for an examiner to conduct various operations.
The examiner can freely move the platform 3 on the base 2 by operating the control lever 4. On the top of the control lever 4, an operation button 4a that is pressed down for requiring execution of production of fundus oculi images is installed.
On the base 2, a post 5 is installed standing upwards. On this post 5, a jaw rest 6 where the jaw of a patient is rested and an external fixation lamp 7 that is a light source for fixing an eye E are provided.
On the platform 3, a main body part 8 is installed to accommodate various optical systems and control systems of the retinal camera 5000. The control system may be installed, for example, inside the base 2 or the platform 3, or in an external device such as a computer connected to the retinal camera 5000.
On the side of an eye E of the main body part 8, an objective lens part 8a disposed facing the eye E is installed. On the examiner's side, an eyepiece part 8b is installed.
Further, to the main body part 8, a still camera 9 for producing a still image of the fundus oculi of the eye E and an imaging device 10 such as a TV camera for producing still images or moving images of the fundus oculi are connected. The still camera 9 and the imaging device 10 are formed so as to be removable from the main body part 8.
As the still camera 9, in accordance with various conditions such as the purpose of an examination and the saving method of produced images, a digital camera equipped with a CCD, a film camera and an instant camera may interchangeably be used appropriately. The main body part 8 is equipped with a mounting part 8c for interchangeably mounting the still camera 9.
In a case where the still camera 9 and the imaging device 10 are for taking digital images, it is possible to transmit and store image data into an image recording device such as a computer connected to the retinal camera 5000.
Furthermore, on the examiner's side of the main body part 8, a touch panel monitor 11 is installed. On this touch panel monitor 11, a fundus oculi image of the eye E formed based on video signals outputted from the (digital-type) still camera 9 or imaging device 10 is displayed. Moreover, on the touch panel monitor 11, an x-y coordinate system taking the center of a screen as the origin is displayed overlapped with the fundus oculi image. When the examiner touches the screen, a coordinate value corresponding to a touched position is displayed.
Next, referring to FIG. 17, a configuration of an optical system of the retinal camera 5000 will be described. The retinal camera 5000 is provided with an illumination optical system 100 that lights the fundus oculi Ef of the eye E, and an imaging optical system 120 that guides the illumination light reflected by the fundus oculi to the eyepiece part 8b, the still camera 9 and the imaging device 10.
The illumination optical system 100 comprises: a halogen lamp 101; a condenser lens 102; a xenon lamp 103; a condenser lens 104; exciter filters 105 and 106; a ring transparent plate 107; a mirror 108; an LCD 109; an illumination diaphragm 110; a relay lens 111; an aperture mirror 1 12; and an objective lens 113.
The halogen lamp 101 is an observation light source that emits continuous light. The condenser lens 102 is an optical element for converging the continuous light (observation illumination light) emitted by the halogen lamp 101 and evenly applying the observation illumination light to the eye E (fundus oculi Ef).
The xenon lamp 103 is an imaging light source that is flashed at the time of imaging of fundus oculi Ef. The condenser lens 104 is an optical element for converging the flash light (imaging illumination light) emitted by the xenon lamp 103 and evenly applying the imaging illumination light to the fundus oculi Ef.
The exciter filters 105 and 106 are filters used at the time of fluorography of images of the fundus oculi Ef. The exciter filters 105 and 106 can be respectively inserted into and removed from an optical path by a drive mechanism such as a solenoid. The exciter filter 105 is placed on the optical path at the time of FAG (fluorescein angiography). The exciter filter 106 is placed on the optical path at the time of ICG (indocyanine green angiography). Hereinafter, an image showing the state of the fundus oculi (blood vessels) of the eye to which a fluorescence agent has been administered will be generically referred to as a “fluorescence image.” At the time of color-imaging, both the exciter filters 105 and 106 are retracted from the optical path.
The ring transparent plate 107 is placed in a conjugating location with a pupil of the eye E, and is equipped with a ring transparent part 107a taking the optical axis of the illumination optical system 100 as the center. The mirror 108 reflects the illumination light emitted by the halogen lamp 101 or the xenon lamp 103, in a direction of the optical axis of the imaging optical system 120. The LCD 109 displays a fixation target (not illustrated) for fixing the eye E.
The illumination diaphragm 110 is a diaphragm member to shut out part of the illumination light in order to prevent flare, etc. This illumination diaphragm 110 is composed so as to be movable in the light axis direction of the illumination optical system 100, and is thus capable of changing an illumination region of the fundus oculi Ef.
The aperture mirror 112 is an optical element that combines the optical axis of the illumination optical system 100 and the optical axis of the imaging optical system 120. In the center region of the aperture mirror 112, an aperture 112a is opened. The optical axis of the illumination optical system 100 and the optical axis of the imaging optical system 120 cross each other at a substantially central location of this aperture 112a. The objective lens 113 is installed in the objective lens part 8a of the main body part 8.
The illumination optical system 100 having such a configuration illuminates the fundus oculi Ef in the following manner. First, at the time of fundus oculi observation, the halogen lamp 101 is turned on and the observation illumination light is emitted. This observation illumination light is applied to the ring transparent plate 107 through the condenser lenses 102 and 104. The light passed through the ring transparent part 107a of the ring transparent plate 107 is reflected by the mirror 108, and after passing through the LCD 109, the illumination diaphragm 110 and the relay lens 111, reflected by the aperture mirror 112 so as to be along the optical axis direction of the imaging optical system 120. Then, the light is converged by the objective lens 113 to enter the eye E, thereby illuminating the fundus oculi Ef.
At this moment, since the ring transparent plate 107 is placed in a conjugating location with the pupil of the eye E, a ring-shaped image of the observation illumination light entering the eye E is formed on the pupil. The entering fundus oculi reflection light of the observation illumination light is emitted from the eye E through a central dark part of the ring-shaped image on the pupil.
On the other hand, at the time of imaging of the fundus oculi Ef, flush light is emitted from the xenon lamp 103, and the imaging illumination light is applied to the fundus oculi Ef through the same path. In the case of fluorography, either the exciter filter 105 or the exciter filter 106 is selectively placed on the optical path, depending on whether FAG imaging or ICG imaging is carried out.
The imaging optical system 120 comprises: an objective lens 113; an aperture mirror 112 (an aperture 112a thereof); an imaging diaphragm 121; barrier filters 122 and 123; a variable magnifying lens 124; a relay lens 125; an imaging lens 126; a quick return mirror 127; and an imaging media 9a. Herein, the imaging media 9a is an imaging media (CCD, camera film, instant film, etc.) for the still camera 9.
The fundus oculi reflection light of the illumination light exiting through the central dark part of the ring-shaped image formed on the pupil of the eye E enters the imaging diaphragm 121 through the aperture 112a of the aperture mirror 112. The aperture mirror 112 reflects cornea reflection light of the illumination light, and acts so as not to mix the cornea reflection light into the fundus oculi reflection light entering the imaging diaphragm 121. As a result, generation of flare on the observation images and produced images is prevented.
The imaging diaphragm 121 is a plate-shaped member having a plurality of circular light-transmitting parts of different sizes. The plurality of light-transmitting parts compose diaphragms with different diaphragm values (F value), and are placed alternatively on the optical path by a drive mechanism (not illustrated herein).
The barrier filters 122 and 123 can be inserted into and removed from the optical path by a drive mechanism such as a solenoid. In the event of FAG imaging, the barrier filter 122 is placed on the optical path, whereas in the event of ICG imaging, the barrier filter 123 is placed on the optical path. Further, at the time of color-imaging, both the barrier filters 122 and 123 are retracted from the optical path.
The variable magnifying lens 124 is movable in the optical axis direction of the imaging optical system 120 by a drive mechanism (not illustrated herein). This makes it possible to change an observation magnifying ratio and an imaging magnifying ratio, and to focus images of the fundus oculi. The imaging lens 126 is a lens that focuses the fundus oculi reflection light from the eye E onto the imaging media 9a. 
The quick return mirror 127 is disposed so as to be capable of being rotated around a rotary shaft 127a by a drive mechanism (not illustrated herein). In a case where imaging of the fundus oculi Ef is performed with the still camera 9, the fundus oculi reflection light is guided to the imaging media 9a by springing up the quick return mirror 127 that is obliquely mounted on the optical path. Meanwhile, in a case where imaging of the fundus oculi is performed with the imaging device 10, or in a case where observation of the fundus oculi is performed with the naked eye of the examiner, the quick return mirror 127 is obliquely mounted on the optical path to upwardly reflect the fundus oculi reflection light.
For guiding the fundus oculi reflection light reflected by the quick return mirror 127, the imaging optical system 120 is further provided with a field lens 128, a switching mirror 129, an eyepiece 130, a relay lens 131, a reflection mirror 132, an imaging lens 133, and an image pick-up element 10a. The image pick-up element 10a is an image pick-up element such as a CCD installed in the imaging device 10. On the touch panel monitor 11, a fundus oculi image Ef imaged by the image pick-up element 10a is displayed.
The switching mirror 129 is rotatable around a rotary shaft 129a in the same manner as the quick return mirror 127. This switching mirror 129 is obliquely disposed on the optical path during observation with the naked eye, thereby reflecting and guiding the fundus oculi reflection light to the eyepiece 130.
When a fundus oculi image is imaged by the imaging device 10, the switching mirror 129 is retracted from the optical path. The fundus oculi reflection light is focused onto the image pick-up element 10a via the relay lens 131, the mirror 132 and the imaging lens 133, and the fundus oculi image Ef′ is displayed on the touch panel monitor 11.
The retinal camera 5000 is a fundus oculi observation device used for observing the state of the surface of a fundus oculi Ef, that is, the surface of the retina. On the other hand, in the deep layer of retina, tissues such as the choroidea and sclera exist. In recent years, a device for observing these deep-layer tissues has been practically implemented (e.g. JP Patent laid-open No. 2003-00543, and JP Patent laid-open No. 2004-52915).
Each of the fundus oculi observation devices disclosed in JP Patent laid-open No. 2003-00543 and JP Patent laid-open No. 2004-52915 is a device (referred to as an optical image measurement device, an optical coherence tomography device, and the like) to which a so-called OCT (Optical Coherence Tomography) technology is applied. Such a fundus oculi observation device is a device that splits low-coherence light into two, guides one (signal light) of the lights to the fundus oculi and the other (reference light) to a given reference object and, based on interference light obtained by overlaying the signal light passed through the fundus oculi and the reference light reflected by the reference object, forms tomographic images of the surface and deep layer tissue of the fundus oculi.
In order to ascertain, in detail, the condition of the fundus oculi (such as the presence or absence of a disorder, stages of progression of a disorder, the degree of therapeutic effect, and the recovery condition), it is regarded as desirable to consider the condition of the surface of the fundus oculi (surface of the retina) and the vicinity thereof (a shallow region under the surface of the retina) and the condition of deeper tissues of the fundus oculi (such as deep tissues of the retina, choroids, and sclera).
However, a retinal camera is a device for obtaining images of the surface of the fundus oculi (such as a color image and a fluorescein fluorescence image), and images of vicinity of the surface of the fundus oculi (such as an indocyanine green fluorescence image). Therefore, it is difficult to ascertain, in detail, the condition of deeper tissues of the fundus oculi, by merely observing an image obtained with a retinal camera. In addition, a considerable amount of skill is required for interpretation, because information overlapping in the depth direction of the fundus oculi is obtained.
Meanwhile, an optical image measurement device is a device for obtaining the tomographic image of the fundus oculi, so that it is difficult to ascertain, in detail, the condition of the surface of the fundus oculi and the vicinity thereof, by merely observing an image obtained with an optical image measurement device. In particular, an image obtained with a so-called Fourier domain optical image measurement device is a tomographic image having a cross section in the depth direction of the fundus oculi, so that it is difficult to ascertain, in detail, the condition of the fundus oculi in a direction of the surface of the fundus oculi.
In addition, in order to comprehensively assess the condition of the fundus oculi, it is regarded as desirable to assess the state of a disease or the like by considering the condition of the surface of the fundus oculi and the vicinity thereof as well as the condition of deeper tissues.
For example, in diagnoses of age-related macular degeneration, newly formed ressels in a choroidal, etc., a fluorescence image of the fundus oculi is useful for observation of the condition of a blood vessel on the surface of the fundus oculi or the vicinity thereof (particularly, comprehension of a leakage condition that cannot be observed on a tomographic image by the optical image measurement device), and a tomographic image by the optical image measurement device is useful in the observation of the condition of a cross section of a retina or a choroid.
In order to enable the diagnoses as described above, it is necessary to present an image obtained by the retinal camera and an image obtained by the optical image measurement device in a display form in which they can be compared with each other. For example, it is desirable to facilitate the comparative work by presenting both the images simultaneously.
In addition, it is desirable to adopt a display form in which the mutual relationship between the image from the retinal camera and the image from the optical image measurement device can be easily ascertained, making it possible to easily perform the comparative work.
In particular, when a site of interest such as an involved are a is specified on one image, it is often desirable to ascertain the condition of the site of interest in more detail by referring to the condition of the site of interest on another image.
However, conventional fundus oculi observation devices cannot easily clarify the mutual positional relationship between an image of the surface of the fundus oculi and the vicinity thereof by the retinal camera and a tomographic image of the fundus oculi from the optical image measurement device, so that it is difficult to ascertain, in detail, the condition of a site of interest.